The present invention relates to a substrate temperature adjustment apparatus in a semiconductor manufacturing system, which performs temperature management for the temperature of a substrate such as a wafer to a certain predetermined value.
Generally, in a semiconductor manufacturing system, semiconductors are manufactured by subjecting a substrate such as a wafer to a plurality of processes, and each process for the wafer is performed under temperature management suitable to it. Since temperatures in the respective processes by each of the units differ, the wafer temperature must be managed in each of the units that perform respective processes and during wafer transfer among the units.
In particular, in a semiconductor exposure apparatus, if the wafer has a nonuniform heat profile, a thermal strain occurs in the wafer, and however good the resolution of the projection optical system is, exposure with a desired line width cannot be performed, and a good overlay accuracy cannot be obtained. For these reasons, wafer temperature management must be performed.
According to a conventional wafer temperature adjustment method, a wafer temperature adjustment time is set for the temperature of a wafer to be loaded. The wafer is kept placed on a wafer temperature adjustment plate for a predetermined period of time, thereby performing wafer temperature management.
Also, according to another wafer temperature adjustment method, the temperature of the wafer is actually monitored, and when the wafer temperature has fallen within a certain predetermined range, wafer temperature adjustment is ended, thereby performing wafer temperature management. This reduces a temperature difference produced on the surface of the wafer.
With the method of performing temperature adjustment of a substrate for a certain predetermined period of temperature adjustment time as with the above conventional temperature adjustment means, the wafer temperature may vary. Hence, when a wafer with a temperature lower than the lower limit of the target temperature range of the wafer is loaded, wafer temperature adjustment is performed more than necessary, and the process speed of the entire apparatus is decreased by the time taken by the temperature adjustment. Conversely, when a wafer with a temperature higher than the upper limit of the target temperature range of the wafer is loaded, the wafer temperature adjustment time becomes insufficient, and the wafer which is not sufficiently temperature-adjusted is processed. This leads to poor precision of the apparatus.
With the method of monitoring the wafer temperature and ending wafer temperature adjustment when the wafer temperature has fallen within a certain predetermined temperature range, it is very difficult to monitor the wafer temperature. With a contact type temperature sensor, in a wafer temperature adjustment unit, since the lower surface of the wafer is brought into contact with the plate, or since the gap between the lower surface of the wafer and the plate is managed, it is very difficult to bring the wafer into contact with the temperature sensor. Also, with a non-contact type temperature sensor, it is difficult to obtain a temperature measurement precision necessary for the wafer. When the substrate temperature adjustment apparatus is provided to a wafer thermometer, the overall size of the apparatus itself becomes undesirably large.
The present invention has been made in view of the above problems, and has as its object to provide a substrate temperature adjustment apparatus for performing substrate temperature adjustment of a substrate, such as a wafer which is being loaded, with an appropriate process time. In other words, it is an object of the present invention to provide a substrate temperature adjustment apparatus for performing temperature control of a substrate to a certain predetermined temperature, in which the temperature of a plate or the like of a temperature adjustment means is measured upon an elapse of a predetermined period of time, and temperature adjustment is performed with a substrate temperature adjustment time determined by the measured temperature of the temperature adjustment means, thereby improving the process speed and temperature adjustment performance.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.